Const::Fast(3pm) - Man pages

Const::Fast(3pm)      User Contributed Perl Documentation     Const::Fast(3pm)

NAME
       Const::Fast - Facility for creating read-only scalars, arrays, and
       hashes

VERSION
       version 0.014

SYNOPSIS
        use Const::Fast;

        const my $foo => 'a scalar value';
        const my @bar => qw/a list value/;
        const my %buz => (a => 'hash', of => 'something');

SUBROUTINES/METHODS
   const $var, $value
   const @var, @value...
   const %var, %value...
       This the only function of this module and it is exported by default. It
       takes a scalar, array or hash lvalue as first argument, and a list of
       one or more values depending on the type of the first argument as the
       value for the variable. It will set the variable to that value and
       subsequently make it readonly. Arrays and hashes will be made deeply
       readonly.

       Exporting is done using Sub::Exporter::Progressive. You may need to
       depend on Sub::Exporter explicitly if you need the latter's
       flexibility.

RATIONALE
       This module was written because I stumbled on some serious issues of
       Readonly that aren't easily fixable without breaking backwards
       compatibility in subtle ways. In particular Readonly's use of ties is a
       source of subtle bugs and bad performance. Instead, this module uses
       the builtin readonly feature of perl, making access to the variables
       just as fast as any normal variable without the weird side-effects of
       ties. Readonly can do the same for scalars when Readonly::XS is
       installed, but chooses not to do so in the most common case. This may
       change in the future if someone takes up maintenance of Readonly, and
       the two modules may be convergence if that happens.

CAVEATS
       Perl doesn't distinguish between restricted hashes and readonly hashes.
       This means that:

        use Const::Fast;
        const my %a => (foo => 1, bar => 2);
        say 1 unless $a{baz}

       Will give the error "Attempt to access disallowed key 'baz' in a
       restricted hash". You have to use "exists $a{baz}" instead. This is a
       limitation of perl that can hopefully be solved in the future.

ACKNOWLEDGEMENTS
       The interface for this module was inspired by Eric Roode's Readonly.
       The implementation is inspired by doing everything the opposite way
       Readonly does it.

AUTHOR
       Leon Timmermans <fawaka@gmail.com>

COPYRIGHT AND LICENSE
       This software is copyright (c) 2010 by Leon Timmermans.

       This is free software; you can redistribute it and/or modify it under
       the same terms as the Perl 5 programming language system itself.

perl v5.34.0                      2022-06-12                  Const::Fast(3pm)

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